Aircraft: EMB ERJ 170/175 ER/LR
Phase of flight: Descent; Initial Approach
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance

We were arriving into LAX from the North; having flown the SADDE6 and receiving vectors for separation and sequencing for a visual approach to Runway 24R under very clear weather. I was Captain and Pilot Monitoring. The First Officer (FO) was Pilot Flying; and was freshly qualified as a line pilot at our airline; having only logged some 25hrs past initial operating experience. ATC on approach frequency advised us of the runway to expect; the traffic we were being sequenced with; and the planned 7 mile final we would be vectored for. The FO was struggling with energy management and vertical navigation using autoflight. We needed to maintain a normal to maybe expedited descent to set up for a stable approach; however; he was choosing modes that kept partial thrust and a slower descent. When given speed reductions; he was leveling off to bleed speed instead of increasing drag to keep descending and slow. I was advising him and running the radio when ATC told us where to find traffic preceding us for the south complex of the airport and to turn to a base heading; descending to maintain 3;000 feet. We were 7nm from the runway threshold. Quick mental math told me we needed to slow and get closer to landing configuration so that we could descend aggressively when allowed to. I suggested this to the FO and while we were configuring; we were told to report the field in sight; which we did. To the best of my recollection; SCT said to us '(Traffic) is for the south complex; Heading 220 to join (final); clear visual approach 24R.' The format of that transmission was exactly the same is it always is; one that I have heard about once or twice a day; 5 days a week now that almost all of our company's flights touch LAX; which is probably why I heard what I expected instead of what was said. I think. At this prompt while on autoflight the pilot flying should arm the intercept for LOC and GS. Instead; the FO armed the NAV function; which-- with a LOC freq tuned in and prior to achieving a heading within 90 degrees of final approach course inbound-- arms the BC approach. I quickly corrected this before the autopilot could start turning us outbound and since the autopilot was also capturing altitude; I selected 2;200 (GS intercept altitude at JETSA) to continue descent and avoid getting too high above glidepath.Just as I was feeling more comfortable with how this approach would turn out; we got the call. SCT asked us; again; 'Do you have the field in sight? You're descending.' This made me uneasy: the implication being that we did not have clearance to descend from 3;000 feet. I replied; again; in the affirmative; and SCT told us to 'Maintain 170 to 5nm final; contact Tower now on 133.9' without ever telling us if we had deviated altitude or not. The flight concluded uneventfully.Assuming that I had erred in maintaining assigned altitude and/or assuming an approach clearance when there was none; there were several factors I recognize as being secondary to the causal problem of task saturation. I think the FO was saturated with trying to maintain the desired flightpath; and I know I was saturated trying to do everything and correct mistakes as they happened. Secondary causes. I was flying with a pilot who has never managed automation before; and was essentially having to teach him the priority logic and how to translate the desired flightpath into something the autopilot could understand. I had only been flying with this pilot for 3 flights; hardly enough to get to know where his strengths and weaknesses were; and how much he could handle. I was predisposed to instructing him and allowing him to continue; since socially it would be a much harsher blow to his ego should I have to take control of the airplane from him.I should have taken the airplane from him; disengaged the autopilot; and asked him to take the radio and confirm our approach clearance. This would have eliminated the then poor translation from human to auto lot; reduced the workload for the FO who is still consolidating the skills acquired during training; and would have eliminated any miscommunication between our aircraft and SoCal approach thereby preventing a pilot deviation from a clearance. An EMB-175 Captain reported a First Officer recently off IOE and new to all automation; had difficulty managing the aircraft's descent and track on a very busy LAX visual approach from over SADDE.